"Membrane roofs" is a general term that may be applied to a low slope or flat roof covered by any means that is intended to produce a continuous waterproof barrier.

Our photo (left) shows roof penetrations and flashing on an EPDM roof in New York. [That chimney may be too short, violating code and safety if it extends less than 2 feet above the roof surface.] Look closely and you can see the marks left by round anchors that tied rooftop insulation to the roof deck below. This telegraphing of insulation fasteners is not a roof defect - it's normal.

Asphalt shingles, in contrast to the EPDM roof shown here, , are not a "waterproof membrane" and depend on the drainage offered by the roof slope to function effectively.

That's why without special measures (discussed at LOW SLOPE ROOFING) we don't expect to find shingles installed on roofs of pitch lower than 4" of rise in 12" of run.

EPDM Roofing Installation & Properties

While a variety of single-ply roofing membranes are used
on commercial jobs, only EPDM has become widely used
on residential sites. EPDM, a form of synthetic rubber,
owes its popularity to its relative ease of installation combined
with exceptional durability. If installed correctly,
roofs often exceed 20 years of service and callbacks are
exceedingly rare.

While some commercial EPDM systems are loose-laid
or ballasted, residential applications are typically fully
adhered. Rolls typically vary from 10 to 50 feet in width
and from 50 to 200 feet in length, but many distributors
will cut a piece to size for smaller jobs. If possible, use a
single piece with no seams for the field of the roof. EPDM
membranes are available in two thicknesses: .045 inch and
.060 inch.

For fully adhered applications or any application
where foot traffic or decking is planned, the thicker
membrane is recommended.

Substrates for EPDM Roofs

EPDM can be bonded to a wide variety of
substrates, including plywood, OSB, fiberboard, and urethane
insulation board. The substrate should be smooth,
even, and free of debris. Fasteners should be driven flush
except in the case of insulation fastening caps, which
project their shape though the membrane. If the surface is
uneven or deteriorated, a layer of fiberboard or thin
plywood should be installed first.

Installation Details for EPDM Roofs

After cutting the material to fit, installers
use a roller to apply a proprietary contact cement to both
the membrane and the substrate. Typically, a length of
roofing is set in place and folded in half lengthwise so one half
can be glued at a time. The adhesive should be fully
dry on both surfaces before bonding, or bubbles may develop.
Also, care must be taken to smooth out wrinkles and
air pockets as the two surfaces are mated. Where seams
are required, the material is lapped 4 to 6 inches and sealed
with either double-faced seam tape or a special adhesive
used for bonding rubber to rubber.

At openings, inside corners, outside corners, and other
irregular shapes where the EPDM roof membrane has been cut, patches
of uncured EPDM are applied using the rubber-to-rubber
adhesive. The uncured form of EPDM is highly elastic and
can be stretched to conform to irregular shapes.

The material is lapped up abutting walls and serves as
its own flashing. Other terminations are usually sealed
with an aluminum termination bar or an aluminum flashing
covered with a strip of EPDM. Finally all exposed
edges of EPDM at laps, patches, and terminations are
sealed with a bead of proprietary caulking that protects the
edge and acts as an extra water stop.
Self-Adhesive.

For small EPDM roof jobs, a few manufacturers
offer a peel-and-stick version of EPDM. Installation is
similar to standard EPDM but may require a primer on plywood
and OSB substrates. Seams generally require a proprietary
adhesive with special caulking on exposed edges.
Although the square foot cost is greater than with site glued
EPDM, on small jobs labor savings offset the higher
material costs.

Pros and Cons of EPDM Roofing

While not intended as a walkway,
EPDM works well as a substrate under rooftop decks. Leftover
strips of membrane should be used to cushion the
roofing from wood sleepers. Leaks are rare and usually can
be traced to sloppy sealing of joints. Leaks are also relatively
easy to identify and fix. One caution is that EPDM
can be damaged by grease and petroleum-based products,
a potential problem with outdoor grills and spillage of
oil-base finishes used on siding or wood decking.

Common Problems in PVC or EPDM Membrane or "rubber" Roofs

As Carson Dunlop's sketch (below) illustrates, wrinkling and failure at seams are problems to watch for where membrane roofs of EPDM, PVC, or similar materials are installed. A wrinkle in an EPDM roof is also shown at the top of this page.

[Click to enlarge any image]

Common EPDM or Rubber Roof Installation or Wear Defects include

Shrinkage and material pulling or even ruptures at flashings if proper allowances were not made during installation

Wrinkles in the rubber roof invite future seam failures

Shown during its 1998 installation at left, this rubber EPDM roof was installed on a New York home by a very large and busy Kingston New York roofing company. We followed the life of this roof and its leak and repair history for the ensuing 12 years and describe the results here.

The roofer also may have been in a bit of a rush. EPDM needs to be opened and allowed to relax before it is installed, and care should be taken to minimize the number and size of wrinkles in the roof during the bonding process.

A few small wrinkles in the center of a section of rubber probably won't cause much trouble, but wrinkles near EPDM roof seams are an other story, as we explain here.

Wrong roof edge flashing causes ponding

The use of an improper drip edge (gravel stop on a roof that did not use gravel ballast) can be seen at the left side of our photo.

The gravel stop "edge flashing" was nailed on top of rather than below the rubber roof material in order to allow the rubber to be lapped over the roof edge and extended an inch into the gutters (not shown) - which was not a bad idea, though the roof's success then depends on the seam sealing tape (not yet installed here) to prevent leaks at the flashing nails.

The problem with using the wrong roof edge flashing ( a flat drip edge should have been installed) was the ensuing ponding at the roof edge. In New York where ponding of melting snow later re-freezes, the freeze/thaw action worked open seams near the roof edge, especially where a wrinkle crossed any roof edge seal or seam tape seal.

The EPDM roof shown above leaked in less than five years, and by ten years of age we found recurrent openings and leak risks at several seams in the roof as well as along the lower roof edge where that stupid gravel stop was installed.

Our photos below illustrate what happens when an EPDM wrinkle extends into a roof seam, and as you can see by the water stains, the gravel stop caused excessive ponding that gave frost extra time to work on and push open the seam tape nearer the roof edge. These seam failures (and leaks) began appearing in the rubber roof in less than five years. The photos below show the roof edge at 14 years of age.

At EPDM ROOF LEAK REPAIRS we describe the maintenance & leak history and the ultimate repairs required for this EPDM roof.

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Technical Reviewers & References

Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com

John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net

The Home Reference Book, a reference & inspection report product for building owners & inspectors.Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.

The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.

Eric Galow, Galow Homes, Lagrangeville, NY. Mr. Galow can be reached by email: ericgalow@gmail.com or by telephone: 914-474-6613. Mr. Galow specializes in residential construction including both new homes and repairs, renovations, and additions.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

Slate Roofs, National Slate Association, 1926, reprinted 1977
by Vermont Structural Slate Co., Inc., Fair Haven, VT 05743, 802-265-4933/34. (We recommend this book if you can find it. It
has gone in and out of print on occasion.)